Scruff Group SG


Premise This group was defined by Herngreen & Wong (1989). The Scruff Group comprises all predominantly marine formations of Late Jurassic - earliest Cretaceous age in the northern Dutch offshore.
Derivatio nominis Named after the offshore Upper Scruff Bank in the North Sea, which lies adjacent to the reference well F03-03. NAM and RGD (1980).
Type section Location map See figure (pdf)
  Well F03-03 (pdf)
  Location N 54°50’45.5
E 04°42’29.3
  Depth 1682 to 2547 m
  Length 865 m along hole
  Reference amended by Munsterman et al. (2012)
Definition Group of formations deposited in a predominantly marine environment. The group consists of a succession of locally bituminous claystones with thin intercalated carbonate beds and glauconitic, sometimes argillaceous, fine- to coarse-grained sandstones.
Upper Boundary The Scruff Group is mildly unconformably overlain by sediments of the Rijnland Group. The upper boundary coincides with the Sequence 3 / Sequence 4 transition (Fig. 2) sensu Abbink et al. (2006). It is associated with the Late Kimmerian unconformity. Generally, a change in colour and log patterns is seen at the contact. As a result of Sub-Hercynian/Laramide inversion tectonics, the Chalk or Lower North Sea groups can also be found overlying this group.
Lower Boundary The group conformably overlies the (paralic to) terrestrial sands of the Schieland Group. Towards the basin margin this contact may become unconformable.
Distribution The group is present in the Step Graben, Central Graben, Schill Grund Platform, Terschelling Basin and in the northern part of the Vlieland Basin (see pdf) .
Age Late Oxfordian - Ryazanian.Late Sequence 1, Sequence 2 and 3 sensu Abbink et al. (2006): Late Oxfordian - Ryazanian.
Depositional Setting The group comprises a variety of Late Jurassic to earliest Cretaceous marine environments from restricted (lagoonal) to open marine (outer shelf) conditions.
Subdivision The Scruff Group is differentiated into two formations:
  SG Scruff Group
  SGLU Lutine Formation (new)
  SGGS Scruff Greensand Formation (amended)
  SGSK Skylge Formation (new)
  SGKI Kimmeridge Clay Formation (amended)
  Here, the Kimmeridge Clay Formation is limited to the northern part of the Dutch Central Graben and Step Graben in late Sequence 1 and Sequence 2 sensu Abbink et al. (2006). The Clay Deep and Schill Grund members are excluded from the Kimmeridge Clay Formation and accommodated in a new formation, the Lutine Formation (Sequence 3). The new Skylge Formation is established to comprise all restricted to shallow marine Late Jurassic succes- sions in the fringes of the Central Graben, Step Graben, Terschelling Basin and northern part of the Vlieland Basin during Sequence 2 sensu Abbink et al. (2006). The Scruff Greensand Formation is restricted to the shallow marine glauconitic sandstones of the northern Dutch offshore in Sequence 3 sensu Abbink et al. (2006).
References See References Upper Jurassic/ Lower Cretaceous